UK light heavyweight Buatsi secured a victory yet underwhelming start to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's activity level likely gained him a judges' verdict in a tight ten-round bout at the Manchester venue.
But Parker landed significant shots, landing some telling individual punches in a match where the techniques didn't complement each other, with excessive holding marring the fight.
Two judges judged it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my best performance but what do champions do? They win," the victor stated in the ring as he was greeted with disapproval from the audience.
The Londoner bounced back after his first professional defeat - an epic battle with his previous opponent in February - to claim a twentieth professional win.
Various analysts thought the challenger, thirty-one, should have been awarded the decision but the Derbyshire fighter endured the second loss of his 28-fight career.
The Champion Earns Win in Slow Match
The fighter's advancement has slowed in recent times through management issues and extended periods of inactivity.
Once tipped as the next star of British boxing, he now is positioned trying to realize his potential - possibly in what appears to be a final roll of the dice - under recent support.
He began cautiously, with both competitors ready to take risks in a cagey early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was competing in only his second appearance at the higher weight class.
By the halfway stage, Parker had made it competitive, making life awkward for Buatsi, who operated with a solid defense to narrowly win the better periods.
The crowd's patience wore thin during regular grabbing, with the challenger going down several times during clinches.
Parker closed well, but multiple periods were challenging to assess. Although, previous titleholder the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, giving Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Inspires Local Rivalry Contest
In the supporting bout, Arthur beat Rea by close verdict in a excellent Manchester vs Manchester fight to secure the European light heavyweight belt.
The stadium became quiet for a extremely emotional homage prior to the bout as a bell ceremony sounded in honor of local hero Hatton, who succumbed 46 years old in September.
It was the initial significant broadcast match card in the city since Hatton's death. As the concluding sound disappeared, the quiet transitioned to a roar of "only one Hatton".
The competition inside the ropes equaled the emotion. Arthur was sent to the canvas by a left hook squarely on the chin in the second round, rising shakily to his feet on the count of eight.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was marked up quickly, significant bruising forming under his face as the duo exchanged hard punches.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with stinging uppercuts as the action rarely dropped over twelve rounds.
Arthur barely secured the decision with official scores of 114-114, narrow lead and wider gap, but both fighters were determined and full of heart, exactly what their idol the legend stood for.
